/*
* Copyright (C) 2011 Google Inc. All rights reserved.
*
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* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
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* its contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
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* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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#include"config.h"
#ifENABLE(WEB_AUDIO)
#include"MultiChannelResampler.h"
#include"AudioBus.h"
namespace WebCore {
namespace {
// ChannelProvider provides a single channel of audio data (one channel at a time) for each channel
// of data provided to us in a multi-channel provider.
class ChannelProvider : public AudioSourceProvider {
public:
ChannelProvider(AudioSourceProvider* multiChannelProvider, unsigned numberOfChannels)
: m_multiChannelProvider(multiChannelProvider)
, m_numberOfChannels(numberOfChannels)
, m_currentChannel(0)
, m_framesToProcess(0)
{
}
// provideInput() will be called once for each channel, starting with the first channel.
// Each time it's called, it will provide the next channel of data.
virtualvoid provideInput(AudioBus* bus, size_t framesToProcess)
{
bool isBusGood = bus && bus->numberOfChannels() == 1;
ASSERT(isBusGood);
if (!isBusGood)
return;
// Get the data from the multi-channel provider when the first channel asks for it.
// For subsequent channels, we can just dish out the channel data from that (stored in m_multiChannelBus).
if (!m_currentChannel) {
m_framesToProcess = framesToProcess;
m_multiChannelBus = adoptPtr(new AudioBus(m_numberOfChannels, framesToProcess));
m_multiChannelProvider->provideInput(m_multiChannelBus.get(), framesToProcess);
}
// All channels must ask for the same amount. This should always be the case, but let's just make sure.
bool isGood = m_multiChannelBus.get() && framesToProcess == m_framesToProcess;
ASSERT(isGood);
if (!isGood)
return;
// Copy the channel data from what we received from m_multiChannelProvider.
ASSERT(m_currentChannel <= m_numberOfChannels);
if (m_currentChannel < m_numberOfChannels) {
memcpy(bus->channel(0)->mutableData(), m_multiChannelBus->channel(m_currentChannel)->data(), sizeof(float) * framesToProcess);
++m_currentChannel;
}
}
private:
AudioSourceProvider* m_multiChannelProvider;
OwnPtr<AudioBus> m_multiChannelBus;
unsigned m_numberOfChannels;
unsigned m_currentChannel;
size_t m_framesToProcess; // Used to verify that all channels ask for the same amount.
};
} // namespace
MultiChannelResampler::MultiChannelResampler(double scaleFactor, unsigned numberOfChannels)
: m_numberOfChannels(numberOfChannels)
{
// Create each channel's resampler.
for (unsigned channelIndex = 0; channelIndex < numberOfChannels; ++channelIndex)
m_kernels.append(adoptPtr(new SincResampler(scaleFactor)));
}
voidMultiChannelResampler::process(AudioSourceProvider* provider, AudioBus* destination, size_t framesToProcess)
{
// The provider can provide us with multi-channel audio data. But each of our single-channel resamplers (kernels)
// below requires a provider which provides a single unique channel of data.
// channelProvider wraps the original multi-channel provider and dishes out one channel at a time.
ChannelProvider channelProvider(provider, m_numberOfChannels);
for (unsigned channelIndex = 0; channelIndex < m_numberOfChannels; ++channelIndex) {
// Depending on the sample-rate scale factor, and the internal buffering used in a SincResampler
// kernel, this call to process() will only sometimes call provideInput() on the channelProvider.
// However, if it calls provideInput() for the first channel, then it will call it for the remaining
// channels, since they all buffer in the same way and are processing the same number of frames.
m_kernels[channelIndex]->process(&channelProvider,
destination->channel(channelIndex)->mutableData(),
framesToProcess);
}
}
} // namespace WebCore
#endif // ENABLE(WEB_AUDIO)